H, 19F and 13C NMR spectra were recorded using a 600 MHz spectrometer (564 MHz

for 19F NMR and 150 MHz for 13C NMR) or a 400 MHz spectrometer (375 MHz for 19

F NMR and 100 MHz for 13C NMR) at 25 °C. Chemical shifts values are given in

ppm and referred to TMS (0.00 ppm) as internal standard. Data are reported as follows: chemical shift, multiplicity (s = singlet, d = doublet, t = triplet, q = quartet, br = broad, m = multiplet). The coupling constants J, are reported in hertz (Hz). High resolution mass spectrometry (HRMS) was obtained on a Q-TOF micro spectrometer. Melting points were determined with a Micromelting point apparatus. TLC plates were visualized by exposure to ultraviolet light. Reagents and solvents were purchased as reagent grade and were used without further purification. All reactions were performed in standard glassware, heated at 70 °C for 3 h before use. Flash column chromatography was performed using silica gel (200–300 mesh).

A 500 mL round-bottomed flask was charged with 2-iodobenzoic acid (20.0 g, 80.64 mmol, 1.0 equiv), finely ground NaIO4 (18.11 g. 84.67 mmol, 1.05 equiv), and 30% aqueous acetic acid (120 mL). The flask was equipped with a reflux condenser and placed in an oil bath preheated to 110 °C. The reaction mixture was allowed to stir at this temperature for four hours at which point the flask was removed from the oil bath and allowed to cool to room temperature. Ice water (100 mL) was added, and the suspension was allowed to stir for 5 min. The fine white needle-like crystals were isolated by S2

Büchner filtration. The crystals were washed with ice water (2 × 100 mL) and dried in vacuo to afford S1 in greater than quantitative yield (contains impurities). In

a

500

mL

round-bottomed

flask

containing

the

crude

1-hydroxy-1,2-benziodoxol-3-(1H)-one (assumed 80.64 mmol, 100% yield for the previous step) was suspended in 56 mL Ac2O. The flask was connected to a reflux condenser and placed in an oil bath preheated to 135 °C. The reaction mixture was stirred for 15 min until most of the solid materials dissolved. The flask was removed from the oil bath and allowed to cool to room temperature, resulting in the formation of white crystals. The flask was then placed in a −20 °C freezer overnight to complete the crystallization. The liquids were decanted and the flask was covered with aluminum foil to protect the product from light. Volatiles were removed in vacuo to afford the product in greater than quantitative yield. To a flame-dried 500 mL round-bottomed flask containing the unpurified 1-acetoxy-1,2-benziodoxol-3-(1H)-one (assumed 80.64 mmol, 100% yield for the previous step) under argon was added anhydrous CsF (0.302 g, 2.0 mmol, 0.025 equiv), CH3CN (170 mL), and TMSCF3 (15.93 g, 16.6 mL, 112 mmol, 1.4 equiv) successively. The reaction mixture was stirred vigorously for 24 h. The white solid suspended in the reaction mixture was then isolated by Büchner filtration. This solid was dissolved in chloroform (300 mL) and any insoluble material was removed by filtration through a cotton plug. The colorless filtrate was then washed with water (200 mL) and sat. aq. Na2CO3 (200 mL). The solution was dried over Na2SO4, filtered and concentrated in vacuo to afford pure 1 (11.07 g, 43%). A second batch of 1 was obtained by concentrating the brown reaction filtrate, dissolving in chloroform (200 mL), washing with water (100 mL) and NaHCO3 (100 mL). The solution was dried over Na2SO4 and concentrated in vacuo to afford a brownish-white solid. The solid was washed quickly in the flask with a small amount of methanol (~20 mL) to remove a large amount of the brown impurity. The resulting solid was then recrystallized from boiling methanol. Cooling to room temperature and placing in a −20 °C freezer resulted in crystal formation. The crystals were collected, washed with cold methanol, and dried in vacuo to provide a second batch of pure 1 (2.58 g, 10% yield). Total yield: 13.65 g (53%). S3

Preparation of substrates 5a–o General procedure 1:

To a solution of ketone S3 (1.0 equiv, 20 mmol) in THF (80 mL) was added methyl dicarbonate (3.0 equiv, 60 mmol) and NaH (2.0 equiv, 40 mmol, 60%). The reaction mixture was refluxed until TLC indicated the total consumption of the ketone. After cooling, the reaction mixture was poured into ice-water (100 mL), acidified with aqueous HCl (3 M) to pH 2~3 and extracted with EA (100 mL × 3). The combined organic layer was dried over Na2SO4 and evaporated under reduced pressure. The obtained β-keto ester S4 (1.0 equiv, 15 mmol) was dissolved in absolute MeOH (60 mL), followed by the addition of ammonium formate (5.0 equiv, 75 mmol). The reaction mixture was stirred under reflux until TLC indicated the total consumption of the β-keto ester and filtered through a short pad of Celite. The filtrate was concentrated in vacuo. To the residue was added water (100 mL), then EA (100 mL × 3) was used to extract the mixture and the organic layer was combined, dried over Na2SO4 and evaporated to dryness. The desired pure product was obtained by silica gel chromatography using a mixture of PE and EA as eluent. Subtrates 5j and 5o were prepared from the commercial 3-oxo-3-phenylpropanenitrile S4-j and methyl 3-oxobutanoate S4-o.

S4

General procedure 2:

The obtained β-keto ester S4 (1.0 equiv, 15 mmol) was dissolved in toluene. To this solution was added DMAP (4-dimethylaminopyridine, 0.1 equiv, 1.5 mmol) and N-methylaniline (1.1 equiv, 16.5 mmol, for S5-k) or n-butanol (1.1 equiv, 16.5 mmol, for S5-l) at room temperature. The reaction mixture was heated to reflux until S4 was comsumed completely. The reaction mixture was cooled to room temperature and the solvent was removed in vacuo. To the residue was added water (100 mL), then EA (100 mL × 3) was used to extract the mixture and the organic layer was combined, dried over Na2SO4 and evaporated to dryness. The desired pure product, S5-k or S5-l were obtained by silica gel chromatography using a mixture of PE and EA as eluent. The obtained S5-k or S5-l (1.0 equiv, 10 mmol) was disosolved in absolute MeOH (40 mL), followed by the addition of ammonium formate (50 mmol). The reaction mixture was stirred under reflux until TLC indicated the total consumption of the substrate and filtered through a short pad of Celite. The filtrate was concentrated in vacuo. To the residue was added water (100 mL), then EA (100 mL × 3) was used to extract the mixture and the organic layer was combined, dried over Na2SO4 and evaporated to dryness. The desired pure product 5k or 5l was obtained by silica gel chromatography using a mixture of PE and EA as eluent. Spectral properties of the substrates 5[1-2] and Togni reagent[3-4] matched the previously reported values.

S5

Preparation

of

β-trifluoromethylated

2H-azirines

7

and

intermediate 6a General procedure

To the enamine substrate 5 (1.0 mmol) dissolved in DCE (10 mL) were added at room temperature Togni reagent 1 (1.2 mmol) and CuI (0.2 mmol). The reaction mixture was heated to 60 °C and progress of the reaction was monitored by TLC. Upon completion, PhIO (1.5 mmol) was added to the mixture and the reaction temperature was maintained at 60 °C. When TLC analysis indicated total comsumption of the formed intermediate 6, the reaction was cooled to room temperature and quenched with saturated aqueous NaHCO3 (30 mL). Then DCM (20 mL × 3) was used to extract the mixture and the combined organic layer was washed with saturated aqueous NaCl (20 mL), dried over Na2SO4 and evaporated to dryness. The desired product 7 was obtained by silica gel chromatography using a mixture of EtOAc/petroleum ether (PE) (10/90, v/v) as eluent.

The procedure of control experiments

Procedure of step I: The enamine substrate 5a (1.0 mmol) was dissolved in DMF (10 mL), then Togni reagent 1 (1.2 mmol) and CuI (0.2 mmol) were added at room temperature. The progress of the reaction was monitored by TLC. Upon completion, the reaction was S6

quenched with saturated aqueous NaHCO3 (30 mL) at room temperature. Then DCM (20 mL × 3) was used to extract the mixture and the combined organic layer was washed with saturated aqueous NaCl (20 mL), dried over Na2SO4 and evaporated to dryness. The desired product 6a was obtained by silica gel chromatography using a mixture of EtOAc/petroleum ether (PE) (10/90, v/v) as eluent.